This application relates to an sensor system that is integrated into a furnace for improving operation of the combustion processes in the furnace, including but not limited to process efficiency, yield, and throughput.
Many industries use oxy-fuel combustion in a furnace for heating of bulk materials or feedstock but often have inadequate means to measure and control furnace parameters in order to optimize the heating processes. It is typical in a variety of industries (e.g., aluminum recycling, steel production, glass manufacturing) to place basic temperature sensors in locations around a furnace dictated by “common sense” or convenience, which often results in measurement errors and lost production capability.
Most typically, the rate of energy input in a heating or melting furnace is controlled based on comparing the temperature measurement of a thermocouple (TC) with a pre-determined setpoint (Tsp). This thermocouple, denoted herein as TOPEN, usually has three characteristics—(1) it is open or exposed to the furnace atmosphere, (2) it is located on a roof or an opposing wall from a burner and (3) it is installed flush with refractory hot face—the combination of which renders the TC susceptible to picking up “direct radiation” from a flame in the furnace just like other surfaces in the furnace (e.g., refractory walls and product surfaces). The charge or product being heated and/or melted is the largest heat sink in the furnace and is able to absorb (at its surface) and conduct (into the body of the charge due to its higher thermal conductivity) the incident energy. However, the refractory wall surface (which has a lower thermal conductivity) and open TC, TOPEN, continue to be radiated upon and increase in temperature. This results in a deviation between the actual product temperature, TPROD, (measured either at the product surface or as an average temperature of the bulk product), and in particular, TOPEN can exceed TPROD by a few or even several hundred degrees. As a consequence, the energy input into the furnace from the burners maybe prematurely decreased because the temperature of the control thermocouple TOPEN reaches the temperature setpoint TSP well before the actual product temperature TPROD, thereby leading to longer heating and/or melting times than desired.